linux-kernel - Re: [PATCH V5 3/4] misc/pvpanic: Avoid initializing multiple pvpanic devices

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Date:   Sat, 16 Feb 2019 14:11:34 +0200
From:   Andy Shevchenko <andy.shevchenko@...il.com>
To:     Peng Hao <peng.hao2@....com.cn>
Cc:     Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        Arnd Bergmann <arnd@...db.de>,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH V5 3/4] misc/pvpanic: Avoid initializing multiple pvpanic devices

On Sat, Feb 16, 2019 at 10:29 AM Peng Hao <peng.hao2@....com.cn> wrote:
>
> Avoid initializing multiple pvpanic devices when configure multiple
> pvpanic device driver type. Make sure that only one pvpanic device
> is working.
>
> Signed-off-by: Peng Hao <peng.hao2@....com.cn>
> ---
>  drivers/misc/pvpanic/pvpanic.c | 13 ++++++++++++-
>  1 file changed, 12 insertions(+), 1 deletion(-)
>
> diff --git a/drivers/misc/pvpanic/pvpanic.c b/drivers/misc/pvpanic/pvpanic.c
> index ccadec0..fbb5038 100644
> --- a/drivers/misc/pvpanic/pvpanic.c
> +++ b/drivers/misc/pvpanic/pvpanic.c
> @@ -15,10 +15,13 @@
>  #include <linux/types.h>
>
>  static struct {
> +       struct mutex lock;
>         struct platform_device *pdev;
>         void __iomem *base;
>         bool is_ioport;
> -} pvpanic_data;
> +} pvpanic_data = {
> +       .lock = __MUTEX_INITIALIZER(pvpanic_data.lock),
> +};
>
>  #define PVPANIC_PANICKED        (1 << 0)
>
> @@ -50,6 +53,12 @@ int pvpanic_add_device(struct device *dev, struct resource *res)
>         struct platform_device *pdev;
>         int ret;
>
> +       mutex_lock(&pvpanic_data.lock);
> +       if (pvpanic_data.pdev) {
> +               mutex_unlock(&pvpanic_data.lock);
> +               return -EEXIST;
> +       }
> +
>         pdev = platform_device_alloc("pvpanic", -1);
>         if (!pdev)
>                 return -ENOMEM;
> @@ -64,9 +73,11 @@ int pvpanic_add_device(struct device *dev, struct resource *res)
>         if (ret)
>                 goto err;
>         pvpanic_data.pdev = pdev;

OK, mutex basically protects pdev member in pvpanic_data. What about
->remove() stage?

> +       mutex_unlock(&pvpanic_data.lock);
>
>         return 0;
>  err:
> +       mutex_unlock(&pvpanic_data.lock);
>         platform_device_put(pdev);
>         return ret;
>  }
> --
> 1.8.3.1
>


-- 
With Best Regards,
Andy Shevchenko